This invention relates generally to dishwasher apparatus and methods for use in cleaning kitchen and dining ware. More particularly, this invention relates to an improved dishwasher system which utilizes ultrasound for effectively and thoroughly cleaning kitchen and dining ware items, in a manner which minimizes the use of water and chemical detergents, and further in a manner substantially eliminating damage to or breakage of fragile items.
Dishwasher systems and methods are well-known in the art for cleaning food debris from kitchen and dining ware items. In particular, known dishwasher systems have commonly relied upon chemical detergents or similar cleaning agents used in combination with heated and/or jetted water to remove food debris from pots and pans, eating and serving utensils, dishware, and cups and glasses, etc. These same principles have been applied uniformly in commercial and institutional eating establishments as well as in a residential environment. In all cases, relatively large quantities of water are required in the course of cleaning and rinsing soiled ware items. In addition, significant quantities of chemical detergents and the like are used. The expended water and chemical detergents, together with food debris removed from the kitchen ware items, are normally discharged to a drain for passage to the local sewage or septic system.
Traditional dishwasher systems and methods of this general type present a variety of limitations and disadvantages which are particularly apparent in commercial or institutional kitchens wherein large quantities of different ware items must be washed on a frequent or near-continuous basis. In such facilities, manual dishwasher techniques involving manual handling and scrubbing of each ware item in a hot water detergent bath are generally being replaced in favor of dishwasher appliances designed to speed the washing process while reducing manual labor requirements and labor costs associated therewith. However, it is widely recognized that many types of food debris such as dried-on or baked-on material are extremely difficult or impossible to remove without individual manual scrubbing of the ware item. Accordingly, while automated dishwasher appliances have provided significant improvements in faster washing with lower labor costs, most commercial and institutional kitchens utilize a pre-rinse station whereat soiled kitchen ware items are manually inspected one at a time, and if appropriate, heavy or stubborn debris is removed with a combination of jetted hot water, detergent, and/or manual scrubbing. As a result, substantial manual labor and related labor costs are still required. Moreover, the requirement for hot water at pre-rinse and wash stations results in high system energy usage. Still further, this requisite manual handling of the individual ware items in a generally wet and slippery environment increases the risk of breakage to fragile glass ware and the like, as well as risk of employee injury upon exposure to broken glass items and/or to the generally wet and slippery work environment.
In addition, increased attention has focused in recent years upon the relatively high usage rate of water and detergent in commercial dishwashing systems inclusive of pre-rinse stations. That is, such dishwashing systems can require several hundred thousand gallons of water each year in a single restaurant establishment, together, with a corresponding usage of several thousand gallons of detergent. This high water use can be extremely undesirable in geographical areas having a limited water supply due to drought or general arid conditions. Moreover, the resultant high rate of discharge of water and chemicals to the local sewage or septic system, particularly in conjunction with large quantities of removed food material, can be extremely undesirable.
Alternative cleaning methods utilizing ultrasound principles are known in the art wherein one or more ultrasonic signal generators provide cavitation bubbles within a water bath for vigorously scrubbing a substrate to be cleaned. More specifically, the ultrasonic generator radiates a high frequency sound wave through the water bath, with the rapidly alternating wave producing a sequence of localized positive and negative pressure regions. The negative pressure regions effectively separate or cavitate the water bath to produce a large quantity of minute bubbles. As these cavitation bubbles within the water bath are contacted against a surface to be cleaned, the bubbles implode and thus provide a substantial mechanical scrubbing action which can be effective in dislodging and removing debris from a submerged target substrate.
Although ultrasonic cleaning systems are applicable in theory for use in cleaning many different types of substrates, including kitchen ware items, attempts to apply ultrasound principles to clean kitchen and dining ware items has not met with success. Instead, breakable kitchen ware items of glass, ceramic and/or similar materials have been highly susceptible to breakage when subjected to ultrasonic cleaning action for even short periods of time. It is believed that the high incidence of kitchen ware breakage in ultrasonic cleaning systems has been attributable to a combination of the highly vigorous bubble scrubbing action and the presence of standing or resonant waves within the water bath.
The present invention overcomes the problems and disadvantages of the prior art by providing an improved ultrasonic dishwasher system designed for effectively and quickly cleaning food debris from a wide and virtually unrestricted range of kitchen and dining ware items, wherein the ultrasonic cleaning action is applied in a regulated manner which substantially reduces or eliminates risk of fragile product breakage. In addition, the ultrasonic cleaning system of the present invention provides effective cleaning of kitchen ware items while substantially reducing requirements for water usage and/or chemical detergents.